In an international passenger airplane (to be simply referred to as an “airplane” hereinafter) or the like, an in-flight entertainment system is mounted to provide an entertainment service to passengers during a long-time flight. In general, a dedicated display terminal is arranged on a rear surface of a backrest of each seat, and headphones can be connected to each seat. In this manner, each passenger can enjoy video contents, audio contents, or games during a flight.
As these video and audio contents, in accordance with various preferences of passengers, programs of as many types as possible need to be prepared to make it possible to continuously provide services during a long-time flight. In this manner, in order to accumulate a large number of contents or distribute contents depending on selection requests from a plurality of passengers, a content distributing server is installed in an airplane.
A basic configuration of a conventional in-flight entertainment system is shown in FIG. 6. Display terminals 221 to 223 are installed in seats 211 and 213, and, at the same time, headphones 231 to 233 are connected to seats 211 and 213. Audio-video contents are accumulated in content distributing server 201 and transmitted to display terminals 221 to 223 and headphones 231 to 233 through network 240. Since the audio-video contents flowing on the network 240 are encoded to compress an amount of information, the audio-video contents are decoded by audio-video decoders (not shown) built in content processing terminals 251 and 253 immediately before the audio-video contents are reproduced by display terminals 221 to 223 or headphones 231 to 233.
On the other hand, the audio-video contents need to be updated into new contents every predetermined period. For example, with respect to movies, an air carrier provides an unreleased movie to passengers as early as possible to differentiate services for passengers. As methods of updating audio-video contents, for example, a method of carrying audio-video contents packaged in an optical disk, a hard disk, a tape, or the like in an airplane to physically exchange the audio-video contents and a method of electrically exchanging (overwriting) audio-video contents through a network are present. Since a recent content distributing server is generally configured by a large-capacity hard disk, in this case, the latter, i.e., electrical updating by a network is used as a general means.
In the updating by a network, in general, contents are uploaded from a content accumulating server on the ground while an airplane is parked. Content accumulating servers holding the same audio-video content are installed in airport facilities, and an airplane can receive a necessary audio-video content even though the airplane is parked in any airport.
A time (upload time) required for uploading is determined by a total volume of audio-video contents to be updated and a speed of a network. For example, when the total volume of the contents and a communication speed are 100 GBytes and 100 Mbps, respectively, an upload time is about 2 hours and 13 minutes. A parking time is determined by a time required for maintenance of an airframe or loading/unloading of cargoes and packages, and the upload time is not preferentially determined. Therefore, when the volume of contents to be uploaded increases, it may be difficult to complete uploading of necessary contents while the airplane is being parked. Furthermore, in terms of improvement of serviceability in an in-flight entertainment system, in the future, a total volume of the audio-video contents may continuously increase. Therefore, it is prospected that updating of audio-video contents is more difficult to be completed while an airplane is parked in one airport.
In this manner, as a countermeasure used when content writing for a mobile object (airplane in the present invention) is not completed during a time for connection to a predetermined base station (airport facility in the present invention), for example, a method is disclosed in Patent Literature 1. In Patent Literature 1, it is supposed that contents are wirelessly transmitted to a mobile object such as trains or automobiles. The contents are written by receiving a radio wave from a specific wireless base station. Since a time in which a mobile object stays in a service area of a wireless base station or a time in which the mobile object passes through the service area is limited, writing of all the contents cannot be completed by only communication from a wireless base station, and only some contents are written. When a plurality of mobile objects that try to receive the same contents, partial contents held by the mobile objects are different from each other. For this reason, when the contents can be transmitted and received between the mobile objects, communication is defined such that shortages in contents of the mobile objects are complementary to each other.
For example, at the present, a mobile object holding only 50% of necessary contents repeats operations of causing the percentage of the contents to reach 70% by content complementarity from a mobile object which the mobile object encounters first and to reach 80% by content complementarity from a mobile object which the mobile object encounters next so that the percentage may reach 100% by performing inter-mobile-object communication several times. When the inter-mobile-object sequential content complementarity is performed, it can be expected that the held contents in the mobile objects gradually increase to complete amounts.
As described above, communication is repeated such that shortages in content between mobile objects holding only partial contents are complementary to each other to make it possible to increase the contents to a complete amount. However, although the method is probably used in a train or an automobile exemplified in Patent Literature 1, it is very difficult to use the method in an airplane which the present invention targets.
More specifically, the chance of causing flying airplanes to come to each other to perform direct wireless communication is rarely present. Even though the airplanes come close to each other to some extent, a communicable time is very short. Most of airplanes are owned by air carriers, and service contents of the air carriers are different from each other, it is actually impossible to hold the same audio-video contents in airplanes of different air carriers. Therefore, content complementarity between mobile objects as described in Patent Literature 1 cannot be applied to airplanes.